Normally speaking, a local courier service that does utilize GPS tracking of their shipments as part of their operations is going to advertise this fact clearly on their webpage. If you read the page or any other marketing materials that the company puts out, then it is probably a safe bet that they don't offer GPS tracking if it is not already mentioned, unless they have just implemented it and have not had a chance to update their marketing materials. GPS tracking is definitely a selling point for a courier, so if they use it, you should expect to hear about it.
If a courier does advertise that they offer GPS tracking on their shipments but you have never done business with them before, be sure to ask if the activation of the GPS tracking feature will mean that you are assessed a surcharge. If a company is new to the technology they may only have a certain number of GPS equipped units that can perform this function, and may charge for its usage. However, a local courier service is required to grant full disclosure of fees, so simply ask and you can be sure you'll get a straight answer.
Many different courier companies will decide for their own reasons whether or not to assess a surcharge for the use of their GPS tracking services on your shipments. This depends on a variety of factors, such as the availability of GPS enabled units, as well as the profit the company feels they could make either way. Some will view the fee as a way to raise charges and profitability, while others will view it as a value added service that will bring them in more customers if they don't pay for it in the long run.
A less reputable courier service that offers you GPS tracking at a fee isn't really offering you something that you need most of the time. Simply enabling the option for GPS tracking isn't likely to either make your delivery much more secure, and certainly will not speed it to its destination. The only time that such a feature might be worthwhile at an added price would be for insurance purposes if you were shipping an incredibly valuable item. Again, these are the sorts of concerns that it is good to bring up with an account representative at your courier company so you know exactly what you will be paying for before the billing is already established for your shipment.